1. Field of the Invention
The invention relates to the field of MOS temperature sensing circuits.
2. Prior Art
It is well-known that metal-oxide-semiconductor (MOS) circuit characteristics widely vary with normal process variations. Moreover, circuit characteristics change considerably with temperature. For this reason, for instance, it is difficult to generate a stable reference potential with an MOS circuit.
Leakage current is one parameter which varies greatly with both process variation and temperature. This current affects the performance of MOS circuits, and by way of example, determines the refresh time in a dynamic access memory. In general, leakage current is considered to be an undesirable chracteristic particularly because of its temperature variations.
The present invention uses the variations of leakage current with temperature to provide a temperature sensing circuit as will be seen. Importantly, the present invention incorporates a second leakage device to cancel the effects of process variations on the leakage current of a first leakage device, thereby providing a circuit with an output substantially dependent only on temperature.